On Sun, Jun 08, 2008 at 07:28:21PM -0700, Joel Becker wrote:> On Sun, Jun 08, 2008 at 02:25:36PM -0700, Luis R. Rodriguez wrote:> > I was really interested in looking to start a filesystem based> > approach for configuration of wireless a while back, an alternative to> > nl80211 if you will, but I stopped after I was told about some major> > issues with configfs. I forget the issues raised clearly so I'd like> > I'd love to hear about the issues as well.

Here's a list of "known" issues I hear about with configfs.These are requests/complaints/etc I have gotten since it was merged.

1) configfs should be sysfs

The argument is that sysfs should somehow support theuser-directed mkdir(2)/rmdir(2) lifecycle of configfs in addition to itsusual functions. This, unfortunately, doesn't work. I sent a prettydetailed discussion of this to lkml the last time it came up, but here'sa short summary. Number one, I tried this first. It got ugly fast.Number two, a goal of configfs is a simpler lifecycle than sysfs(understanding the lifetimes of config items). Adding an additionalmode to the already complicated lifecycle of kobjects directly opposesthis

2) There needs to be a way to pin a config item

configfs's ->drop_item() operation returns void - if it iscalled, your item must deactivate. This is in line with configfs'user-directed paradigm. However, sometimes another kernel subsystem isdepending on that item - it will crash if the item goes away. After getting this beaten over my head a few times by goodfriends, I realized they were right. configfs now hasconfigfs_depend_item() to allow subsystems to pin config items whennecessary.

3) configfs should support large attributes

A configfs attribute can be a maximum of 4k in size. This fitsthe simple show/store methods cribbed from sysfs. However, more thanone person has given a good reason for larger attributes, often lists ofthings. This isn't implemented yet, because I haven't come up with agood way to do it. seq_file works pretty well for the show side, butthere is no seq_write() to match on the store side. I'd love to come upwith a sane semantic and make it work. Consider it a TODO.

Finally, this thread has presented 4) easier definition of items, perhaps with macros like DEFINE_ATTR

I think I have a __CONFIGFS_ATTR() macro, but it's nowhere nearas nice as what sysfs has. This definitely could use some work, makingconfigfs easier to use.

That's what I have. I don't know if any of these issues werewhat you were worried about, Luis.